The FCC has informed me that it is not against FCC regulations for Sonic to block the harasser's telephone number from the entire Sonic network. The FCC has advised me that I should file a complaint against Sonic with the FCC.
A carrier cannot simply block a telephone number carrier-wide at the request of one of our customers. That's simply not permitted, despite what someone at the FCC might tell you over the phone. The only scenario where I see that being possible is if we were to receive an order from a court that required us to do that - but even this would be subject to regulatory oversight, and could be overturned by the FCC or CPUC.
Again, I would suggest you consider a couple things:
First and foremost, report the incidents to the police, and then seek a protective order that bars the person from calling you. This will give you some recourse if they continue. If they do continue, you could then seek an order to their carrier to disconnect their service, or arrest, depending upon the severity of the situation.
Second, get a telephone that lets you block calls from their number. I provided a link to one option, here's that again: https://www.amazon.com/dp/B01HXMJ14S/re ... MBbV2QVNMJ
Finally, this could become a legitimate safety issue for you, and public discussion forums are not the best place for you to try to seek a solution. This is a law enforcement issue and you really must contact them.